How do you stop an 83 430WR pinging?

I have only just found this forum and am hoping somebody out there can give me some suggestions on how to stop my 1983 430WR from pinging in 4th, 5th and 6th gears.

So far I have tried the following:
1. Made a 0.9mm copper head gasket (stopped pinging but lost power)
2. Retarded ignition timing (also stopped pinging but lost power)
3. Tried main jets up to the ID of the needle jet and then tried a larger needle jet (also stopped pinging but then wouldn't rev out cleanly)

The motor has been given a mild professional port job (polishing rather than timing), Boysen reeds and is run on 100 octane with synthetic oil.

There is some very minor dinging in the dome of the head when a piece of piston ring broke off during a seizure but I have smoothed that off as much as possible.

The NGK BR8EG plug is a dark tan after a 3 km run at 120kph on a mild spring day.

The power through the first 3 gears is great but the pinging starts when reving into the top end in 4th and gets worse in 5th and 6th.

I was going to try and pick up another head on Ebay as a last resort just in case the minor dinging is causing hot spots.

Any sensible suggestions will be much appreciated.........

Never had any pinging issues myself. I bought new bike a number of years ago and thought it pinged but in the end it was chain slap. Probably not applicable but I note that. Did you polish the head or make it more shiny? There has been suggestions that polishing the head is no good as it reflects heat as well as some of the local hillclimbers who turned pro in years gone by have said they roughed up the combustion chamber as part of their race mods. How about adding some race gas? I have added a bit or high lead race gas before oil went to $140 a barrel and race gas got real expensive and never came back down. I was just hoping the lead might somehow counter the effects of the alcohol. Not sure how octane is computed where you are or if you have alcohol. Pinging is the fuel air charge flashing into flame instead of the flame starting at the spark plug and spreading out in predictable manner. I usually associate pinging with low rpm and high load though I seem to be able to use poorer gasoline than the manual says on most all of my two wheeled vehicles over the years.

Fran

Have you checked the squish band clearence ?

I have managed to find a head in excellent condition which should turn up in the next 2-3 weeks.

The squish band clearance is not something I had considered as it won't have changed from new but I will check it out anyway.

I am able to get 100 octane unleaded fuel here so the fuel should not be a factor.

I suspect that the polished ports and Boysen reeds are delivering more mixture to the combustion chamber than standard and this is the root of the issue. Maybe I could try a thinner copper head gasket as the first one was fairly thick and noticeably reduced the compression ratio. This would also correct any problem with the squish band clearance if it exists.

Could the increased breathing of the motor actually require a larger carburettor that is able to deliver more fuel?

The ports are significantly bigger in the water cooled version and it has the same carburetor. Those things don't have head gaskets do they? You vary the the base gasket to get the desired squish though there isn't a choice in the parts book. New bikes have a lot of choices of base gasket thicknesses. What I seem to recall reading on this site is putting a piece of soft solder in the squish area and squishing it and measuring it. You could try and search out that thread. I might try and use clay or something else 50-50 lead tin solder doesn't seem that soft to me.

Fran

Here are some articles on Squish Band Clearence and how to test.
http://www.gasgasrider.org/html/measuring_squish.html
http://www.rb-designs.com/

I would almost suspect an ignition problem. You blast through the first three gears pretty fast but fourth through sixth slower. In that time you could have a ignition/coil problem causing bad timing?

Another thought- your silencer isn't plugged up is it???

The pipe and silencer are very clean.

The stator and coil have been swapped while the issue has been happening. The SEM stators did not seem to be very reliable and I had 2 fail so this time I got a custom made one from Electrexworld in the UK which is working well. Adjusting the timing definitely has an effect but the detonation doesn't go away until the power drops off.

I will see how the replacement head goes and then try a thinner head gasket than the first 0.9mm one I made. Maybe 2 base gaskets would have a similar effect although that would change the port timing a bit.

Also got some 0.3mm copper sheet on the way to make up a thin head gasket. These don't have a head gasket as standard and I recall that I have lapped the top of the cylinder liner several times in the past to get a good seal to the head. Maybe the lapping has reduced the squish band clearance enough to cause detotation?

So did any of those bad experiences involve the engine running real fast and wouldn't shut off no matter what and you didn't think about kicking it into gear?

I searched out the thread I was thinking of. The gaskets it speaks of apparently aren't in the on line shopping inventory. Apparently varying thicknesses can be obtained from the aftermarket.
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I am not so sure the port timing is going to change a lot if the squish is the pinging culprit and only the minimum adjustment is make. One could also see if the top of the piston lines up with the bottom of the exhaust port at bottom dead center just to see if something is a little strange or not.

If say the rod bearing was just about to go and was loose would the piston fly up farther or would the compression keep that rolling bearing in compression?

Fran

There is no play on the big or little end as it was rebuilt only about 2000km ago.

I'm thinking its running Lean. Except for Your Spark Plug reading of Dark Brown. You said that You went to a Larger Needle. If the Diameter is Larger then its going to block off more Fuel and run Leaner. A smaller Needle would alow more Fuel. A lot of Dirt Bikes run fine with Black Spark Plug readings. Your probably way ahead of me on this one but sometimes the simpleist Fixs are the hardest to see.

Actually I went to a larger needle jet to allow more fuel through. It ended up not revving cleanly through the top end so I eventually got too much fuel through.

I am still hoping a 0.3mm copper head gasket and replacement head will cure the problem. The 0.9mm gasket I made up knocked off too much compression and reduced the power significantly.

The bits should turn up it the next couple of weeks.

Daltex,
Perhaps you could post your jet numbers?
Also, could you do a compression test to see where you are? Hold the throttle wide open and kick until you can't breathe. It takes a while to max out the gauge.

Adding a head gasket might (might) be working against you, since opening up that squish distance can lead to poor flame control and worse pinging. Admittedly, I haven't had to try that on a 430 so I can't say for sure. Rather, I'd like to see what happens with squish in the .045-.055" range, good jetting, a full-flowing fuel system (check inside), and timing about 2.0mm BTDC.

And, not to insult, but are you SURE that what you're hearing is pinging?

OK today I made up a 0.22 mm thick head gasket and fitted another head that has a perfect surface on the dome and squish area. I also fitted a low-time 38mm Mikuni taken from a 430XC. I still have to get the jetting right (it's now a little rich) but at least the pinging has stopped. It looks like I possibly have taken too much off the top of the liner when lapping it to seal against the head and there may have also been some pre-ignition from the small indentations in the dome and squish caused by debris from the previous ring breakage/seizure. The timing is still the standard 2.2mm BTDC. I will lean it off a bit and see if the pinging has really gone when the motor is revving out in 5th and 6th.

That sounds like a good step in the right direction. 430's are SO fun when they're running right. I would do two things next:

1. Compare every piece of brass in the two carbs and see if there are any differences. In particular, make sure the "lean" carb has a 3.3 needle/seat in it (it's stamped in tiny letters, but they do wear off). Also make sure it's got the R-0, R-2, or R-4 needle jet in it. Husky did send out a few 430's with Q-8's (although I can't remember if that was an 81, 82 or 83 goof) and that was too small.

2. The other thing, just so you know where you are, is to check the squish. I can't stress enough just how POORLY the 430's vary here.

I stripped the original carby to find a Q-8 needle jet, 6DH3 needle and 3.3 float valve/seat.

The needle jet size would explain why going up on the main jets seemed to have little effect. I thought that I had put a larger needle jet in a few years ago but I must have just replaced it with the same size because I still have the original and it is also the Q-8.

Ahhh... the plot thickens. It's always encouraging when you find something that 'might' be the problem! And what needle jet is in the carb that works?